Detection rate of prostate cancer using prostate specific antigen in patients presenting with lower urinary tract symptoms: a retrospective study.

BACKGROUND: Need for undertaking prostate biopsies for detection of prostate cancer is often decided on the basis of serum levels of prostate specific antigen (PSA). AIM: To evaluate the case detection rate of prostate cancer among patients presenting with lower urinary tract symptoms (LUTS) on the basis of PSA levels and to assess the scope of prostate biopsy in these patients. SETTING AND DESIGN: A retrospective study from a tertiary care center. MATERIALS AND METHODS: The clinical and histopathological data of 922 patients presenting with LUTS in the last five years was obtained from the medical record section. They had been screened for prostate cancer using PSA and /or digital rectal examination examination followed by confirmation with prostate biopsy. STATISTICAL ANALYSIS USED: Detection rate and receiver operating characteristic curve were performed using SPSS 16 and Medcalc softwares. RESULTS: The detection rate of prostate cancer according to the PSA levels was 0.6%, 2.3%, 2.5%, 34.1% and 54.9% in the PSA range of 0-4, 4-10, 10-20, 20-50 and> 50 ng/ml, respectively. Maximum prostate cancer cases were detected beyond a PSA value of 20 ng/ml whereas no significant difference in the detection rate was observed in the PSA range of 0-4, 4-10 and 10-20 ng/ml. CONCLUSION: A low detection rate of prostate cancer observed in the PSA range of 4-20 ng/ml in LUTS patients indicates the need for use of higher cutoff values of PSA in such cases. Therefore we recommend a cutoff of 20 ng/ml of PSA for evaluation of detection rate of prostate cancer among patients presenting with LUTS.

Conformation and interaction with the membrane models of the amino-terminal peptide of influenza virus hemagglutinin HA2 at fusion pH.

Conformations of a 48-mer peptide corresponding to the amino-terminal region of influenza HA2 in aqueous and membranous environments were studied. In aqueous solution the peptide was found to be oligomeric and its helicity was enhanced at higher concentrations. The conformation in phospholipid bilayer and insertion depth into the sodium dodecyl sulfate (SDS) micelle for the fusion peptide were in line with those determined for the amino-terminal 25-mer analog. The turn of residues 28-31 found in the crystal structure of hemagglutinin at neutral pH persisted in the presence of SDS at pH 5.0. Except for the turn, conformational lability of the amino portion of HA2 is suggested by comparison of the secondary structure determined herein with that obtained with the influenza fusion protein crystallized in the aqueous phase at neutral pH. The backbone amide proton exchange experiment suggested an interaction with the micellar surface for the segment carboxy-terminal to the fusion peptide domain.

An archaeal photosignal-transducing module mediates phototaxis in Escherichia coli.

Halophilic archaea, such as Halobacterium salinarum and Natronobacterium pharaonis, alter their swimming behavior by phototaxis responses to changes in light intensity and color using visual pigment-like sensory rhodopsins (SRs). In N. pharaonis, SRII (NpSRII) mediates photorepellent responses through its transducer protein, NpHtrII. Here we report the expression of fusions of NpSRII and NpHtrII and fusion hybrids with eubacterial cytoplasmic domains and analyze their function in vivo in haloarchaea and in eubacteria. A fusion in which the C terminus of NpSRII is connected by a short flexible linker to NpHtrII is active in phototaxis signaling for H. salinarum, showing that the fusion does not inhibit functional receptor-transducer interactions. We replaced the cytoplasmic portions of this fusion protein with the cytoplasmic domains of Tar and Tsr, chemotaxis transducers from enteric eubacteria. Purification of the fusion protein from H. salinarum and Tar fusion chimera from Escherichia coli membranes shows that the proteins are not cleaved and exhibit absorption spectra characteristic of wild-type membranes. Their photochemical reaction cycles in H. salinarum and E. coli membranes, respectively, are similar to those of native NpSRII in N. pharaonis. These fusion chimeras mediate retinal-dependent phototaxis responses by Escherichia coli, establishing that the nine-helix membrane portion of the receptor-transducer complex is a modular functional unit able to signal in heterologous membranes. This result confirms a current model for SR-Htr signal transduction in which the Htr transducers are proposed to interact physically and functionally with their cognate sensory rhodopsins via helix-helix contacts between their transmembrane segments.

The leucine zipper motif of the envelope glycoprotein ectodomain of human immunodeficiency virus type 1 contains conformationally flexible regions as revealed by NMR and circular dichroism studies in different media.

A 43-mer peptide derived from the coiled coil domain of the transmembrane glycoprotein, gp41, of human immunodeficiency virus type 1, was synthesized. Light scattering measurements suggested that the peptide molecules likely exist in the aqueous solution in trimeric form. Circular dichroism experiments showed a moderate helix population enhancement for the peptide in 80% methanol solution relative to helicity in sodium dodecyl sulfate micellar suspension. NMR spectroscopy indicated that the N-terminal section of the peptide was conformationally more sensitive to the medium. The conformationally labile regions contain residues implicated in gp41-gp120 association. Our data support the idea that the coiled coil region is responsible for oligomerization of the gp41 ectodomain and suggest a site of conformational isomerization following receptor binding-induced gp120 dissociation from gp41.

Fusion induced aggregation of model vesicles studied by dynamic and static light scattering.

Membrane fusion is a key step in the virus mediated cell fusion. The vesicular dispersion serves as a model system to study the membrane fusion. We employed dynamic and static light scattering to study the fusion of phosphatidylcholine vesicles in the presence of model fusion peptide fragments from the hemagglutinin HA2 protein. The fusion-induced aggregation under the present experimental setup exhibited strong pH dependence, similar to the parental viral protein. Replacement of the glycine residue at the extreme amino terminus by glutamic acid (G1E) abolished fusion activity. The average molecular mass and diameter of vesicular dispersion obtained from static and dynamic light scattering measurements respectively at neutral and acidic pH showed about three fold increase in acidic solution containing wild type fusion peptide. The light scattering data are consistent with lipid mixing results. The present work demonstrates the utility of light scattering as a facile means to monitor the fusion process.

Proline inhibits aggregation during protein refolding.

The in vitro refolding of hen egg-white lysozyme is studied in the presence of various osmolytes. Proline is found to prevent aggregation during protein refolding. However, other osmolytes used in this study fail to exhibit a similar property. Experimental evidence suggests that proline inhibits protein aggregation by binding to folding intermediate(s) and trapping the folding intermediate(s) into enzymatically inactive, "aggregation-insensitive" state(s). However, elimination of proline from the refolded protein mixture results in significant recovery of the bacteriolytic activity. At higher concentrations (>1.5 M), proline is shown to form loose, higher-order molecular aggregate(s). The supramolecular assembly of proline is found to possess an amphipathic character. Formation of higher-order aggregates is believed to be crucial for proline to function as a protein folding aid. In addition to its role in osmoregulation under water stress conditions, the results of this study hint at the possibility of proline behaving as a protein folding chaperone.

Detection and assay of proteases using calf lens beta-crystallin aggregate as substrate.

The eye lens protein, betaL-crystallin, aggregates and yields a turbid solution upon refolding from its denatured state. We have observed that the addition of trace amounts of protease results in clearing of this turbidity. Based on this observation, we have developed a simple and rapid method for the detection and assay of proteases. This assay can be performed in the pH range of 6.0-9.0. We could assay the activity of trypsin at a concentration as low as 5 microg/ml.

Molecular basis of indomethacin-human serum albumin interaction.

Studies on the strength and extent of binding of the non-steroidal anti-inflammatory drug indomethacin to human serum albumin (HSA) have provided conflicting results. In the present work, the serum-binding of indomethacin was studied in 55 mM sodium phosphate buffer (pH 7.0) at 28 degrees C, by using a fluorescence quench titration technique. The interaction of indomethacin with human serum albumin has been studied as a function of temperature, ionic strength and pH. The results suggest that electrostatic interaction plays a major role in the binding. The possible role of lysine residues in this interaction was studied by modifying exposed and buried lysine residues of HSA with potassium cyanate and studying indomethacin binding with the modified HSA. The data suggest that the interaction takes place via a salt bridge formation between the carboxylate group of indomethacin and a buried lysine residue of HSA. A technique involving fluorescence enhancement of bilirubin upon its interaction with HSA was used to study its displacement by indomethacin. The displacement, although apparently competitive in nature, was not strong suggesting that the primary sites of interaction of bilirubin and indomethacin are different.

Biophysical characterization of the structure of the amino-terminal region of gp41 of HIV-1. Implications on viral fusion mechanism.

A peptide of 51 amino acids corresponding to the NH2-terminal region (5-55) of the glycoprotein gp41 of human immunodeficiency virus type 1 was synthesized to study its conformation and assembly. Nuclear magnetic resonance experiments indicated the sequence NH2-terminal to the leucine zipper-like domain of gp41 was induced into helix in the micellar solution, in agreement with circular dichroism data. Light scattering experiment showed that the peptide molecules self-assembled in water into trimeric structure on average. That the peptide molecules oligomerize in aqueous solution was supported by gel filtration and diffusion coefficient experiments. Molecular dynamics simulation based on the NMR data revealed a flexible region adjacent to the hydrophobic NH2 terminus of gp41. The biological significance of the present findings on the conformational flexibility and the propensity of oligomerization of the peptide may be envisioned by a proposed model for the interaction of gp41 with membranes during fusion process.

Primary adenocarcinoma of the urinary bladder: a study of 6 cases from the pathologist's point of view.

OBJECTIVE: The clinical presentation of adenocarcinoma is not different from the usual transitional cell carcinoma, hence the histological diagnosis plays an important role in the interpretation of cystoscopic biopsies. Six cases of primary adenocarcinoma of the urinary bladder are described from the pathologist's point of view. The diagnostic problems encountered in these cases are highlighted. METHODS: 6 cases of primary adenocarcinoma of the urinary bladder were encountered from 1983 to 1997. Relevant clinical data were analyzed. Multiple sections from the tumor and adjoining areas of the bladder were studied. Five patients were aged 50 to 75 years and the youngest patient was 22 years old. RESULTS: Hematuria and retention of urine were common presenting symptoms. Histologically, the diagnostic problems faced were mucinous metaplasia vs mucinous carcinoma, clear cell adenocarcinoma of the urinary bladder vs clear cell carcinoma of the pelvic kidney. We had one case of urachal and 5 cases of non-urachal carcinoma. CONCLUSIONS: Primary adenocarcinoma of the urinary bladder is an unusual tumor accounting for 0.5 to 2% of all bladder malignancies. They are commonly seen in endemic areas like schistosomiasis. By origin they are grouped into urachal and non-urachal carcinoma and histologically grouped as enteric, mucinous, clear cell and adenocarcinoma not otherwise specified. Direct consultation with the urologist, clinical findings, investigations and careful screening of histological material will help the pathologist to arrive at a correct diagnosis.

Proline affects oligomerization of a coiled coil by inducing a kink in a long helix.

The structural effect of a proline in a helix in trifluoroethanol (TFE)/water medium was examined on a 29-mer peptide and its proline analog derived from the leucine zipper (LZ)-like motif of gp41 (the transmembrane glycoprotein of HIV-1) by NMR and circular dichroism (CD) spectroscopies. Lower helical content was found for the proline mutant from the CD study. NMR data show that distortion of the helix by proline is local and occurs mainly on the N-terminal side of the substitution site. Molecular dynamics computation exhibits a bending of the helical axis of 30 degrees +/- 10 degrees, in agreement with X-ray diffraction results. Light-scattering experiments indicated that the average aggregation number of the proline-substituted mutant is substantially lower than that of the wild-type peptide. From the ratio of dissociation constants of the wild-type and the proline mutant peptides, the difference in free energy of trimeric formation is calculated to be 2.1 kcal/mol. Thermal stability, helicity, and the average aggregation number for the helix oligomers were found to be correlated. The structural alteration and the reduced coiled coil stability may account for the deficiency in the biological functions of the proline mutants of gp41 and in the inhibitory action of proline-substituted peptides. These effects may also be important in unraveling the roles played by proline in transmembrane proteins.

Structural perturbation of alpha-crystallin and its chaperone-like activity.

alpha-Crystallin is a multimeric lenticular protein that has recently been shown to be expressed in several non-lenticular tissues as well. It is shown to prevent aggregation of non-native proteins as a molecular chaperone. By using a non-thermal aggregation model, we could show that this process is temperature-dependent. We investigated the chaperone-like activity of alpha-crystallin towards photo-induced aggregation of gamma-crystallin, aggregation of insulin and on the refolding induced aggregation of beta- and gamma-crystallins. We observed that alpha-crystallin could prevent photo-aggregation of gamma-crystallin and this chaperone-like activity of alpha-crystallin is enhanced several fold at temperatures above 30 degrees C. This enhancement parallels the exposure of its hydrophobic surfaces as a function of temperature, probed using hydrophobic fluorescent probes such as pyrene and 8-anilinonaphthalene-1-sulfonate. We, therefore, concluded that alpha-crystallin prevents the aggregation of other proteins by providing appropriately placed hydrophobic surfaces; a structural transition above 30 degrees C involving enhanced or re-organized hydrophobic surfaces of alpha-crystallin is important for its chaperone-like activity. We also addressed the issue of conformational aspects of target proteins and found that their aggregation prone molten globule states bind to alpha-crystallin. We trace these developments and discuss some new lines that suggest the role of tertiary structural aspects in the chaperone process.

Interaction of bromocresol green with different serum albumins studied by fluorescence quenching.

The binding of bromocresol green to bovine serum albumin at micromolar concentrations leads to quenching of protein fluorescence. This property has been used here to study interaction of bromocresol green with bovine serum albumin as a function of pH and ionic strength. The transformation of fluorescence quench data obtained with bromocresol green into Scatchard plots yielded an association constant of 3.06 x 10(7) 1 M-1 and a binding capacity of about 1.0. The affinity of bromocresol green for bovine serum albumin remains virtually unchanged between pH 4.0 and 8.0 but decreases by about 7 fold with increase in ionic strength from 0.01 to 1.0. Six other serum albumins obtained from cat, dog, human, pig and sheep have also been studied for bromocresol green binding. Although all the albumins studied bind bromocresol green, they show considerable differences in their affinities towards the dye. It appears that despite a great degree of overall similarity in their structure and conformation, serum albumins from different species differ in their ligand binding properties.

On the role of lysine residues in the bromophenol blue-albumin interaction.

In order to explore the role of buried lysine residues of bovine serum albumin (BSA) in its interaction with bromophenol blue (BPB), three acetylated derivatives of albumin namely: 90%, 100% and 10%/chiefly having modification of buried lysine residues) were prepared by conventional and double modification techniques. The modification of lysine residues resulted in the change in conformation, as evidenced by the increase in Stokes radius from 3.55 nm (for native albumin) to 4.91 and 4.97 nm for 90% and 100% acetylated albumins, respectively. Modification of buried lysine residues (10% acetylated preparation) of albumin increased the Stokes radius up to 3.96 nm. The interaction of BPB with albumin preparations was studied spectrophotometrically at ionic strength 0.4 and at three different pH values i.e., 4.0, 6.0 and 8.0. There was decrease in BPB binding on increasing the modification. A decrease of 63% and 69% was noticed at pH 8.0 in 90% and 100% acetylated preparation, respectively. The 10% acetylated BSA preparation with minimum conformational changes also showed a significant decrease (31%) in BPB binding at pH 8.0. The change in Kd from 2.04 x 10(-6) M for native albumin to 5.41 x 10(-6) M for 100% acetylated albumin and 3.39 x 10(-6) M for 10% acetylated preparation at pH 8.0 confirmed the critical role of buried lysine residues in BPB-BSA interaction.

Co-refolding denatured-reduced hen egg white lysozyme with acidic and basic proteins.

Refolding of denatured-reduced lysozyme and the effect of co-refolding it with other proteins such as RNase A, bovine serum albumin, histone, myelin basic protein, alcohol dehydrogenase and DNase I on the renaturation yield and the aggregation of lysozyme have been studied. Basic proteins consistently increase the renaturation yield of the basic protein lysozyme (10-20% more than in their absence) with little or no aggregation. On the other hand, co-refolding of lysozyme with acidic proteins leads to aggregation and a significant decrease in renaturation yields. Our results show that hetero-interchain interactions (non-specific interactions) occur when the basic protein lysozyme is refolded together with acidic proteins such as bovine serum albumin, alcohol dehydrogenase or DNase I. Our results also suggest that the net charge on proteins plays a significant role in such non-specific aggregation. These results should prove useful in understanding the hetero-interchain interactions between folding polypeptide chains.

Gastrostomy without laparotomy--a percutaneous endoscopic technique: review of 35 cases.

Percutaneous endoscopic gastrostomy (PEG) was performed in 33 patient with head injury, one with laryngeal cancer, and one with gastric volvulus. The gastrostomy tube was prepared from 20 F Foley catheter and a plastic micropipette tip. The complications encountered included peritubal leak in three patients (9%) and abdominal wall hematoma in one patient (3%). There was no procedure-related mortality. We recommend PEG for tube enteral feeding in patients who have lost the swallowing reflex.

Metronidazole ("Flagyl") in dracunculiasis: a double blind study.

Two-hundred and twenty-nine cases dracunculiasis were selected for a double-blind trial of metronidazole against placebo. A cure rate of 85% was observed with metronidazole. A dosage of 400 mg metronidazole three times daily for 10-20 days appears suitable. Even with secondarily infected lesions, it was unnecessary to administer any other chemotherapeutic agent. In most cases symptomatic relief, especially of pain and pruritus, was obtained within two weeks. In patients with only subcutaneous worms, metronidazole did not apparently prevent the development of lesions and seemed to stimulate the worm to emerge quickly, with resultant less severe lesions. Complete cure was delayed in patients with multiple lesions, where worms reached the emergence state at different times. There did not appear to be any direct relationship between severity of the disease and response to metronidazole. If the worm was broken during treatment with metronidazole, no abscess formed nor was there any local inflammation. Metronidazole was very well tolerated even when administered for 20 to 25 days. No serious side-effects or toxic effects were observed.